(Bloomberg) -- The Philippines said a Chinese Navy ship entered waters within the archipelago without permission earlier this year, potentially expanding a territorial dispute beyond the South China Sea. 

The ship lingered in the Sulu Sea, which is surrounded by undisputed territory in the Philippine archipelago, for three days from late-January to early-February despite being challenged by a Philippine Navy vessel, the Southeast Asian nation’s Department of Foreign Affairs said in a statement Monday. The Chinese vessel reached waters of Palawan’s Cuyo Group of Islands and Apo Island in Mindoro south of Manila, it said.

The Chinese ship’s actions “did not constitute innocent passage and violated Philippine sovereignty,” the department said. Foreign Affairs Undersecretary Ma. Theresa Lazaro issued a demand for Chinese Ambassador Huang Xilian to follow international law and stop Beijing’s vessels from entering Philippine waters uninvited, according to the statement.

The Chinese Embassy in Manila didn’t immediately respond to a request for comment.

The Philippines has been locked in a dispute with China over parts of the South China Sea, with Manila repeatedly protesting Beijing’s presence in the contested waters.

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